Miggy,
You will be unable to work in the US as an LPN. You need to have an RN in order to be sponsored for a green card. I would highly recommend that you go for the RN, as they are being fast-tracked for green cards in the US, if that is where you really wish to work. Your only chance of working in the US as an LPN is if you marry an American, or marry someone that already has a green card.
Canada is also going to be the same for you. Many of the provinces are actually going to be requiring for you to have a BSN to be permitted to practice there.
Taking the exams as listed by the other poster should be the furthest thing from your mind right now. There are many other steps to be accomplished beforehand.
You will need to complete a full set of English exams, with skills in speaking equivalent to those of a native speaker. You may want to concentrate on that right now.
Hope that this helps and good luck with your studies..............